Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. During the process, the primary effluent is taken to aeration tank that contain large number of aerobic heterotrophic microbes. They form flocs that digest a lot of organic matter. As the biological oxygen demand of waste water is reduced, it is passed into settling tank to undergo sedimentation. The sediment of the settling tank is called activated sludge that is a rich source of aerobic bacteria. Hence, the statement (d) is correct. Biogas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. It is made up of methane, carbon dioxide with traces of nitrogen, hydrogen sulphide and hydrogen. Methanobacterium is an anaerobic bacterium that is found in rumen of cattle and is helpful in the breakdown of cellulose.

Correct Option: D

Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. During the process, the primary effluent is taken to aeration tank that contain large number of aerobic heterotrophic microbes. They form flocs that digest a lot of organic matter. As the biological oxygen demand of waste water is reduced, it is passed into settling tank to undergo sedimentation. The sediment of the settling tank is called activated sludge that is a rich source of aerobic bacteria. Hence, the statement (d) is correct. Biogas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. It is made up of methane, carbon dioxide with traces of nitrogen, hydrogen sulphide and hydrogen. Methanobacterium is an anaerobic bacterium that is found in rumen of cattle and is helpful in the breakdown of cellulose.

Organic farming involves use of organic wastes and other biological material along with beneficial microbes to release nutrients to crop to increase the soil fertility in an ecofriendly, and pollution tree environment. Glomus, earthworm and Oscillatoria can be used in organic farming while snail cannot.

Correct Option: D

Organic farming involves use of organic wastes and other biological material along with beneficial microbes to release nutrients to crop to increase the soil fertility in an ecofriendly, and pollution tree environment. Glomus, earthworm and Oscillatoria can be used in organic farming while snail cannot.

Azotobacter is a free living soil bacterium able to take up dinitrogen from the soil and fix it into organic nitrogenous material like aminoacid. Clostridium is anaerobic free living soil N₂ fixing bacteria. Rhizobium is symbiotic N₂ fixing bacteria.

Correct Option: C

Azotobacter is a free living soil bacterium able to take up dinitrogen from the soil and fix it into organic nitrogenous material like aminoacid. Clostridium is anaerobic free living soil N₂ fixing bacteria. Rhizobium is symbiotic N₂ fixing bacteria.

A common biocontrol agent for control of plant diseases is Trichoderma. Trichoderma is a tree living fungus that exert biocontrol over several plant pathogens for the control of plant diseases. It is the natural method of pest and pathogen control.

Correct Option: D

A common biocontrol agent for control of plant diseases is Trichoderma. Trichoderma is a tree living fungus that exert biocontrol over several plant pathogens for the control of plant diseases. It is the natural method of pest and pathogen control.

Agrobacterium is a soil borne pathogen responsible for affecting many higher species of plant. But Rhizobium, Nostoc and Mycorrhiza are biofertilizers.

Correct Option: A

Agrobacterium is a soil borne pathogen responsible for affecting many higher species of plant. But Rhizobium, Nostoc and Mycorrhiza are biofertilizers.